Triple Bandpass Filters
Triple Bandpass Filters allow us to go above and beyond traditional Normalized Difference Vegetation Index (NDVI) indicators to reinvent the way we monitor crop health. Traditionally, true NDVI was used to determine plant health, which incorporates a camera with a red + NIR filter and the equation NDVI = (NIR – Red) / (NIR + Red).
Scientific advances have found that modifying this calculation can provide more details about crop and field health. Similarly to red light, healthy plants absorb blue light. In addition to NIR light, healthy plants reflect some green light.
With this knowledge, MidOpt designed two Triple Bandpass Filters, which allow one camera to gather data results at all three wavelengths, making them an affordable, lightweight alternative to aerial surveillance applications that otherwise might require 3+ camera sensors.
1) TB550/660/850 Green + Red + NIR This filter takes traditional red + NIR measurements to a whole new level by adding green. Green + Red + NIR wavelengths are used for applications where Chlorophyll Vegetation Index (CVI), Normalized Green (NG) and other vegetative index monitoring is needed. Two of the calculations used are CVI = (NIR x Red) / (Green ^ 2) and NG = Green / (NIR + Red + Green).
2) TB475/550/850 Blue + Green + NIR Use of the 475nm, 550nm and 850nm wavebands differ from earlier calculations, because it uses Blue + Green + NIR light instead of red. This method is recognized as the Enhanced Normalized Difference Vegetation Index (ENDVI), a technique that can provide more detailed information. ENDVI may better isolate plant health indicators and can generate results and false color mapping to indicate values as far down as the pixel level. The ENDVI formula is ENDVI = ((NIR + Green) – (2 x Blue)) / ((NIR + Green) + (2 x Blue)).
Triple Bandpass Filters are offered in various standard threaded mounts and custom mounts that are cut to fit any lens or camera. Standard material thicknesses are 0.5mm, 1.1mm and 2mm.
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